Frequency multiplier



E. G. LINDER FREQUENCY MULTIPLIER Juan. 5, 1943.

Filed April 50, 1941 2 Sheets-Sheet l Jan. 5, 1%43. G. UNDER 2,307,693

FREQUENCY MULTIPLIER Filed April 30, 1941 2 Sheets-Sheet 2 I Zmnentor Patented Jan. 5, 19453 FREQUENCY IVHILTIPLIER Ernest G. Linder, Philadelphia, Pa, assig'nor to Radio Corporation of America, a corporation of Delaware 9 Claims.

This invention relates to an improvement in frequency multipliers and particularly to an improved ultra high frequency device in which target electrodes are arranged in echelon to multiply the frequency of currents applied to a control electrode.

Numerous types of electronic frequency multipliers are known to those skilled in the art. In some of these devices the movements of electrons are phased so that they give up their energy to electrodes connected to tank circuits. In other devices electrons are directed through resonant cavities in which they create standing waves. In the instant invention pulses of electrons are applied to echelon electrodes which are connected to or form resonant circuits. The pulses, arriving at the echelon electrodes at different times, create resonant currents in the resonant circuits.

An object of the present invention is to provide improved means for frequency multiplying. An other object is to provide means whereby pulses of electrons may be converted into ultra high frequency currents of a frequency higher than the frequency of said pulses. Another object is to provide means for applying pulses of elec trons to echelon target electrodes so that the input frequency is multiplied in the output circuit including said electrodes.

The invention will be described by referring to the acompanying drawings in which Fig. 1 is a schematic illustration of one embodiment of the invention; Fig. 2 is a graph illustrating the mode of operation; Fig. 3 is a schematic diagram of a push-pull arrangement of the invention; Fig. 4 is a schematic diagram of an embodiment of the invention in which the echelon target electrodes form the resonant circuits; Fig. 5 is an end view of the echelon electrodes of Fig. 4; Fig. 6 is a graph representing the current or potential distribution on the target electrodes of Fig. 5; Fig. 7 is a schematic diagram of a modification of the invention; and Fig. 8 is a graph illustrating the push pull mode of operation. Similar reference characters will be applied to similar elements in the drawings.

Referring to Fig. 1, within an evacuated envelope l are arranged a cathode 3, a control electrode 5, a hollow cylindrical accelerating electrode l including a grid or aperture, and echelon target electrodes 9, H. The target electrodes are connected to a resonant and symmetrically arranged transmission line iii. A magnetic focusing field is established by a solenoid IE or like source. cathode is connected through a biasing battery ii to ground. The hollow cylindrical electrode 7 including a grid at one thereof and the target electrodes are maintained at suitable positive potentials by means of a battery It. An oscilla- The connections are as follows: The

tor 2!, or other source of currents whose frequency is to be multiplied, is connected between the cathode 3 and control electrode 5.

The mode of operation is as follows: Electrons emitted from the cathode 3 are directed toward the target electrodes 9, H. Groups of electrons are emitted under the control of the potentials applied to the control electrode 5. The variation of the control potential may be of the form illustrated by the curve A of Fig. 2. Some of the electrons will first meet the electrode 9 nearer the cathode and will deliver their energies to establish pulses or half cycles of current as represented by B of Fig. 2. If the resonant line length 93 is properly chosen and if the farther electrode I l is suitably spaced, for example a distance corresponding. to the transit time of a quarter period of the oscillator 2! frequency, then pulses or half cycles of current as at C will be delivered by the electrons reacting the farther electrode a quarter cycle later in time. Since the pulses B and C are applied to the opposite terminals of the resonant line, it follows that B and C will be of opposite phase and, therefore, will combine as shown at D. The intervening broken line portion of the graph D represents the sustained oscillations established in the resonant line. It may be noted that the oscillation D in the output or resonant circuit l3 are of a higher frequency than the applied oscillations A. While the foregoing illustrates frequency doubling it should be understood that the frequency may be multiplied by any integer.

The arrangement illustrated by Fig. 3 is difierent from that of Fig. 1, in that push pull connections are used in the former. A pair of cathodes 3, 3' and a pair of control electrodes 5, 5 are used. A pair of echelon target electrodes, consisting of a plurality of step-like surfaces 9, H and 9', ll and arranged at diiferent distances from the cathodes, are connected to the resonant line. The portions 8, 9' and H, H of the electrodes normal to the electron movements are spaced so that portions 9 and 9' are a distance corresponding to the transit time of a half cycle of the input frequency; portions H and H are also a distance corresponding to the transit time of a. half cycle; and portions 9 and H are spaced a distance corresponding to the transit time of a quarter cycle along the electron paths. Thus arranged each input pulse produces two output pulses and the frequency is multiplied by four in the output circuit.

In the operation of the push pull device the oscillator 2i applies currents out of phase to the control grids 5 and 5. These currents alternately group the electrons which are directed to the target electrodes. The target electrodes are so spaced that the current pulses A9, BH,

A9 and Bi l as shown in Fig. 8 are app-lied to the resonant circuit to establish therein an oscillatory current of a frequency higher than the oscillator frequency.

For optimum operation the echelon target electrodes should be of dimensions and spacings small compared to the operating wave length. For high degrees of frequency multiplication, or at extremely short wave lengths, it may not be practical to design sufficient small electrodes and to provide proper spacings. One arrangement for overcoming these difficulties is illustrated in Fig. l. In this arrangement the electrons are emitted from a cathode 3| extending across the envelope 33. The control electrode 35 and accelerating electrode 31 are positioned near the cathode and between the cathode and the echelon target electrodes 39, 6|. he target electrodes form the resonant circuit. Fig. 5 shows the end view of the target electrodes and Fig. 6 represents the potential distribution on the resonant line formed by the electrodes. The operation of the arrangement of Fig. 4. is essensentially the same as that of Fig. 1 except that the accelerating electrode 37 is in the form of a grid in Fig. 4.

Grid electrodes may be introduced for various purposes. For example, in Fig. '7 grid electrodes 63 have been introduced in front of the target electrodes. In other respects the arrangement of Fig. 7 corresponds to that of Fig. 3. The grid electrodes are connected to a switch it so that they may be connected to a point on the battery l9 as positive as the accelerating anode, or to a point less positive, or the grid may be connected through modulating means M to the battery it. If the grids are made less positive, they slow down the electrons and reduce the heating effect of the electrons impinging on the target. If the grids are made more positive and are secondarily emissive, electron multiplication will be obtained. If modulating voltages are applied, the output currents may be modulated in any desired manner.

Thus the invention has been described as an ultra high frequency device in which electrons are emitted in pulses or groups. The electrons impinge upon target electrodes in echelon. The impinging electrons arrive at different sections of the target electrodes at different times Whereby currents of different phases are established. The target electrodes are a part of the resonant circuit in which oscillations are established. These oscillations are of a higher frequency than the pulse or group frequency. Several apparatus arrangements for carrying out the described method of frequency multiplication are illustrated. The output currents may be applied to a suitably coupled load circuit.

I claim as my invention:

1. An ultra high frequency device including in combination a source of electrons, means for grouping said electrons, a resonant circuit including pairs of target electrodes arranged in echelon and of opposite instantaneous polarity at the resonant frequency of said circuit, and means for directing said groups of electrons onto said target electrodes so that currents of a frequency higher than the grouping frequency are established in said resonant circuit.

2. An ultra high frequency device including in combination a source of electrons, means for grouping said electrons at a predetermined rate, a resonant circuit including pairs of echelon target electrodes, and an accelerating electrode for directing said groups of electrons onto said target electrodes so that oscillatory currents of a frequency higher than said predetermined rate are established in said resonant circuit.

3. An ultra high frequency device including in combination a source of electrons, means for grouping said electrons at a predetermined rate, and a pair of echelon target electrodes, each of said electrodes consisting of a plurality of steplike surfaces arranged at different distances from said source, said electrodes being juxtaposed and connected together to form a resonant circuit, and an electrode including means for accelerating said groups of electrons so that they impinge on said pair of target electrodes to establish resonant currents in said circuit.

4. An ultra high frequency device including in combination a source of electrons, an electrode for controlling said electrons, means for applying controlling voltages to said electrode to group said electrons, means for accelerating said group electrons, a pair of echelon target electrodes, each of said electrodes being formed of step-like surfaces, differently spaced from said source, a resonant line having its terminals of opposite potential connected to said target electrodes, and means for applying said accelerated electrons to said target electrodes so that said groups reach said targets at different phases so that currents are alternately established at the opposite terminals of said resonant circuit.

5. A device of the character of claim 1 including a grid electrode arranged between said source and said target electrodes to control the grouped electrons directed onto said target electrodes.

6. A device of the character of claim 3 including a grid electrode arranged between said source and said target electrodes to control the grouped electrons impinging on said target.

7. An ultra high frequency device including two sources of electrons, means for alternately grouping the electrons from said sources, a resonant circuit including target electrodes arranged in echelon, and means for directing said alternately grouped electrons onto said target electrodes so that currents of a frequency higher than said grouping frequency are established in said resonant circuit.

8. A device according to claim '7 including a control electrode positioned between said sources and said target electrodes for controlling the alternately grouped electrons directed onto said targets.

9. An ultra high frequency device including in combination a source of electrons, means for grouping said electrons into groups corresponding to alternate cycles of said grouping means, a pair of echelon target electrodes, each of said electrodes including a plurality of step-like surfaces arranged at different distances from said source and further arranged to form a resonant circuit, and means for directing said grouped electrons onto said target electrodes so that oscillation currents of a frequency higher than said grouping frequency are established in said resonant circuit.

ERNEST G. LINDER. 

